Cupolas

ABSTRACT

Combustion gases are generated in the liquid fuel combustion chambers provided on the middle shell of a cupola and blasted on the red-hot coke which is supplied automatically below said combustion chambers, to generate gas mixtures consisting of CO, H2 and N2 by water gas reaction and reducing reaction. These gas mixtures can be used as useful heat sources. By this process, the steam which has been so far regarded as a taboo in cupola operations can advantageously be utilized as hot gas so that cast iron of superior quality may be produced with better yields.

[451 May 2, 1972 United States Patent Takahashi et al.

[54] CUPOLAS Williamson............

Tokyo; Yoshimi Okawara, Kawasaki-shi, all of Japan [72] inventors: Akira Takahashl, Kita-Adachi-gun,

Saitama-ken; Aldmasa Arata,

Primary Examiner-Gerald A. Dost [73] Assignee: Miiuji Iron Works Co., Ltd., Tokyo, Japan Attorney-McGleW and Toren [22] Filed: Oct. 22, 1969 ABSTRACT Combustion gases are generated in the liquid fuel combustion chambers provided on the middle shell of a cupola and blasted on the red-hot coke which is supplie said combustion chambers, to generat ing of CO, H, and N d automatically below e gas mixtures consistby water gas reaction and reducing reacres can be used as useful heat sources. By am which has been so far regarded as a rations can advantageously be utilized as [21] Appl.No.:

[30] Foreign Application Priority Data June 4, 1969 Japan....t.....t........................44/442ll tion. These gas mixtu this process, the ste iron of superior quality may be produced Wt 08 amm n u .m w Owen .m O 10 0 h hm. mhw 503 204 ZHM v 5 3F? 4 l o n 5 anon 0 m ms 6 MR m 2 m L w '0 smu UIIF 1]] 218 555 [[l 2 Claims, 2 Drawing Figures t a a Patented May 2, 1972 3,659,832

INVENTORS AKIRQ TQKQHDSHI AKIMASQ ARQTR YOSHIMI OKQWF'RQ ATTORNEYS CUPOLAS SUMMARY OF THE INVENTION This present invention relates to cupolas operated by joint use of coke and liquid fuel as heat source.

In the conventional cupola, in order to obtain cast iron of superior quality, efiorts have been made to use coke of high grade and to dehumidify the blown air, thereby to prevent, as much as possible, steam from entering the cupola, so that the charged pig iron may be melted in the reducing atmosphere. In a cupola using only coke, combustion has to be controlled mainly by the volume of air to be introduced through tuyeres, and there have been witnessed a difiiculty for operators to acquire special skills of such. controlling and also a disadvantage that the manufacturing cost of cast iron products is in upward tendency due to the recent rise in prices of high grade coke.

In order to eliminate such defects as mentioned above, to increase productivity as well as melting speed and further to reduce the consumption of coke, there has been proposed a method for utilizing liquid fuel in addition to coke. For example, a liquid fuel is burnt in the special combustion chambers provided outside of the cupola so as to have hot gases created and blown into the cupola, or to have hot blasts created by mixing such hot gases with air to be sent in through tuyeres and then blown into the cupola. This method may help the melting speed increase but it has a fundamental defect that the steam generated by the combustion of liquid fuel is made contact with and oxidizes the melted iron, resulting in producing cast iron of inferior quality only.

An object of the present invention is to provide an improved method for melting pig iron and an improved cupola for carrying out said method and another object is to provide method of melting pig iron for producing cast iron of superior quality with good yields.

The object of the invention can be accomplished by a method comprising making the gases generated by the combustion of a liquid fuel contact with the red-hot coke in a cupola at areas outside of the melting zone and also outside of the area into which melted iron falls from said melting zone, and making them into non-oxidizing hot gas mixtures of CO, H and N by water gas reaction and reducing reaction, and then supplying these gas mixtures to the melting zone. Another object of the invention can be accomplished by a cupola comprising equipping the cupola which consists of three separate parts, lower, middle and upper, the middle part being placed atop the lower part and having a form of shell diverging wider as it extends from bottom upward to head, and the upper part, whose shell gradually widens as it extends from head downward to bottom, being arranged so that its lower portion intrudes down to a certain depth into the middle part, and also providing liquid fuel combustion chambers in between the overlapped shells of said middle and upper parts.

According to the present invention, in order to have raw materials melted in the cupola by the heat generated by the combustion of coke and liquid fuel, the hot gases generated by the combustion of the liquid fuel make contact with the redhot coke so that the so-called water gas and reducing reactions may occur, thereby generating CO, H and N and introducing the mixture thereof into the melting zone. Thus, according to the invention, the steam which has been so far regarded as a taboo in cupola operations can be advantageously utilized as hot gas so that high quality cast iron may be produced with better yields. Further, for this purpose, at suitable places on the middle shell are provided liquid fuel combustion chambers, and from their lower open ends the combustion gases are discharged and blown into direct contact with the red-hot coke. In this case, the red hot coke which is consumed in the reducing reaction is to be moved into the right place and replenished automatically.

The liquid fuels used in the present invention may be any of such generic ones as heavy oil, coal tar, oil tar, methane gas, propane gas, etc. However, from a standpoint of economy and ease in handling, coal tar or heavy oil is recommended.

For one illustration of the practice of the present invention, reference should be had to the accompanying drawings, in which:

FIG. 1 is a schematic view in longitudinal section of the eupola, and

FIG. 2 is a schematic view in cross section on axis A-A' of FIG. 1.

The cupola according to the present invention is comprised of three different parts, i.e., the lower part formed of a shell 1, the middle part formed of a shell 2 and the upper part formed of a shell 3. The shell 2 of the middle part is so formed that it diverges wider as it extends from bottom upward to head. The upper part with the shell 3 is placed and fixed above the middle part with the shell 2 in such a manner that the lower portion of the former intrudes into the latter; and in between the upper portion of the shell 2 and the lower portion 4 of the shell 3 there are provided liquid fuel combustion chambers 5. Below each combustion chamber 5 is a sufiiciently wide opening 6, and red-hot coke is forced into this opening, consumed and replenished constantly and automatically by the pressure of raw materials supplied into the cupola. Atop each of these chambers 5 there are equipped a control valve 7 and a heavy oil burner 8. To the control valve 7 preheated air is supplied from an air preheater 9 through a pipe 10; and to the heavy oil burner 8 is connected a pipe 12, to which heavy oil is supplied through valves 1 1.

Further, according to the invention, the inside diameter d, of the upper part with the shell 3 at the upper portion is smaller than that d at the lower end, such diameters becoming gradually greater as the shell extends from about the middle portion down to the lower end. This is so designed as not to have melted iron fall along the inner peripheral surface of the shell but to have it fall down vertically.

Next, the mode of operations of the cupola according to the present invention will be described. The cupola is sufficiently dried up and then charged, through the charging mouth 13, and loaded with cokes to such extent that they reach as high as about the middle level of the melting zone. Thereafter, air is introduced into the cupola, through a plurality of tuyeres 16, which are arranged with equidistance and in symmetry on the wall of the lower shell 1 by way of the pipe 14, the air preheater 9 and the pipe 15, and at the same time compressed air and heavy oil are supplied through the pipe 10 and pipes 12, respectively, to the heavy oil burners 8 which are then ignited.

In the above illustrated embodiment, air is introduced into the cupola through a branch of pipe at the place 17, originated from a single air-blowing system. Such air blowing, if so required, may be done from different systems, independent each other. Thus, when the bed charge of coke is sufficiently burnt, a tap 18 is closed, and through the charging mouth 13 are charged base metals together with flux such as limestones, fluorspars, soda ashes, etc., continuously and in layers. The hot gases generated by the combustion of heavy oil in the combustion chambers 5 come into contact with the red-hot coke 19 contained below the combustion chambers 5 so that both water gas reaction and reducing reaction may start. As a result, the high temperature steam generated by combustion is decomposed into high temperature I-I, gases and carbon monoxide (CO) by water gas reaction, and at the same time the high temperature CO gases generated by combustion of heavy oil are partly reduced and decomposed into CO and CO Thus generated C0, C0 and H gases are mixed with N gases of high temperature, and form mixtures of non-oxidizing high temperature gases, which are blown further into the cupola. The steam which has not reacted with the red-hot coke 19 below the combustion chambers 5 finish reacting completely as they move upward along the inside wall of the upper shell 3. Moreover, because of the divergence in the diameters at the middle and lower portions of the upper shell 3 as described above, there is no fear that said ascending steam might contact with and oxidize the following melted iron.

In the foregoing description of the embodiment of the present invention, as shown in FIG. 2, the liquid fuel combustion chambers 5 are arranged one each on both sides of the cupola, but it is understood that the invention is not limited to this arrangement and that three or more may be provided as needs demand.

The distinguishing advantages derived by the present invention may be given as that there is no fear that cast iron would be deteriorated in quality by the steam generated by liquid fuel combustion, and that since the combustion gases of the liquid fuel supplies heat, the melting period will be reduced and the consumption of coke may also be reduced, and further that the liquid fuel combustion can be controlled with ease so that cast iron of superior quality may be produced easily in large quantities.

The invention is further illustrated by the following examples.

Referring to FIG. 1 of the drawings, the inside diameter of the lower part with the shell 1 near the tuyeres 16 was set at 300 mm; the middle shell 2 was diverged and expanded right and left upward between the 470 and 710 mm levels high from the level of the tuyere 16; the upper shell 3 was arranged to intrude into the middle part with the shell 2, so as to provide spaces for two right and left combustion chambers 5, and further the perpendicular length of the opening 6 below the combustion chamber was set at 300 mm. In this cupola there was charged an amount of 35 kg of materials consisting of steel scraps in 30 percent, pig iron in 35 percent and circulating material in 35 percent for a single turn of operations. These operations were repeated twice. The results are shown in Table 1 (Example Nos. 1 and 2).

Samples of gas from the melting zone were collected at three different times through a sampling hole provided on the middle shell, and analyzed. The results of the analysis are shown in Table 2 (Example Nos. 1, 2 and 3). In these two Tables, the figures in the Comparison" column relate to an example in which only coke was used.

TABLE 1. OPERATING CONDITIONS AND DATA Iron charged (Kg) Burner 595 1050 665 Ratio ofcoke (36) 8.6 11.0 17.0 Ratio of heavy oil 61.9 33.8 0 (liter/metric ton) Melting speed( kg/hr) 370 410 300 Melted iron 1,400-1 ,500 l,400-l,500 1,450-1 ,540

temperature C) TABLE 2. ANALYSES OF GASES IN CUPOLA (AT 1. A cupola, for producing cast iron by burning coke to melt iron-containing charges in a melting zone supplied with air under pressure, said cupola comprising, in combination, a lower section, an intermediate section, and an upper section, superposed in vertical alignment with each other; said intermediate section comprising a shell diverging upwardly to form a first shell portion whose cross-sectional area is substantially greater than that of said upper section and said lower section; said upper section comprising a shell including a second shell portion projecting into said first shell portion and defining therewith laterally projecting combustion chambers, said second portion of said upper section gradually widens downwardly; means supplying non-solid fluid fuel and air to said combustion chambers for combustion of the non-solid fuel therein to produce combustion gases; means directing said combustion gases into contact with the incandescent coke in a zone extraneous to the melting zone, which is in said upper section, and outside the path of molten iron falling from the melting zone, to produce non-ozidizing gas mixtures of CO, H and N through the water-gas and reducing reactions; and means directing the non-oxidizing gas mixtures upwardly through said upper section into the melting zone.

2. A cupola for producing cast iron, as claimed in claim 1 in which the inside diameter of said upper section at its upper part is less than its inside diameter at its lower part, the inside cross-sectional area of said upper section gradually increasing downwardly in said shell portion of said upper section. 

2. A cupola for producing cast iron, as claimed in claim 1, in which the inside diameter of said upper section at its upper part is less than its inside diameter at its lower part, the inside cross-sectional area of said upper section gradually increasing downwardly in said shell portion of said upper section. 